Adds a new member for an XID - either an addressable member such as a
wallet, or an installation acting on behalf of an address.
A key-pair that has been associated with one role MUST not be permitted to be
associated with a different role.
Changes the recovery identifier for an XID. The recovery identifier is not required
to be a member of the XID. In addition to being able to add members, the
recovery identifier can also revoke members.
The first entry of any XID log. The XID must be deterministically derivable
from the address and nonce.
The recovery address defaults to the initial associated_address unless
there is a subsequent ChangeRecoveryAddress in the log.
An existing address on xmtpv2 may have already signed a legacy identity key
of type SignedPublicKey via the ‘Create Identity’ signature.
For migration to xmtpv3, the legacy key is permitted to sign on behalf of the
address to create a matching xmtpv3 installation key.
This signature type can ONLY be used for CreateXid and AddAssociation
payloads, and can only be used once in xmtpv3.